Barry Daniels wrote:The really fine stuff does not settle for a long time. An air filtration with a two stage filter has a much better chance of removing the sub micron level particles than a box fan with a simple house filter, or even the Filtrete or similar fabric filters.

I'm using the 3M Filtrete MPR 2800 "Ultrafine" 20x20 pleated hvac filters which capture down to 0.3 micron and pre-filter with a less effective/cheaper hvac filter to catch the large stuff. There was a study published in one of the woodworking magazines a while back reviewing air cleaners and included this set-up in the review. It worked as well as the others but needed longer to reach the same particle counts in the test shop as the larger units. Using it directly behind hand sanding work, time doesn't factor into my use because of the low volume of contaminated air directly at the intake of the fan. I also like being able to bring it in the house when the shop is too cold or hot and be able to work comfortably at the dining room table w/o spreading dust inside.

Barry Daniels wrote:The thicker the filter, the better. That 5" should be effective.

HEPA filters are rated to remove 99.97% of particles that have a size down to 0.3 µm. And it's the sub micron stuff that cause the most problems because they get further down into your lungs.

Good point, Barry. That's another reason why I'm doing more with hand tools over time. I'm also using a P100 mask when I do really dusty things and I'll be looking for better ways to have cleaner air as I do more in the shop.

I checked my filter and is it rated to 0.3 microns. It's not the full HEPA of 99.97% but at 95% it is not bad at all. My shop's air is not dusty and I am not coughing when I'm out there. I think my cheap solution is much better than nothing and might not be much worse than the expensive ones after all.

Eric, actually that filter rating is not that great, if you look at it like this: The difference between 99.97% and 95% is pretty large. One allows 0.03 percent through and the other lets 5% through, which is 167 times more. Of course, these numbers may not actually represent what is going on with your specific setup.

I see personal protection as something that most everyone can improve over time as you gear up. Just budget PPE into your shop expenditures to allow it to keep up with, or even get ahead of your expanding tool inventory and your time spent in the shop.